=> select version(), postgis_full_version(), postgis_raster_lib_version();
PostgreSQL 9.1.5 on x86_64-pc-linux-gnu, compiled by x86_64-linux-gnu-gcc
(Gentoo 4.4.6-r1 p1.0, pie-0.4.5) 4.4.6, 64-bit | POSTGIS="2.0.1 r9979"
GEOS="3.3.3-CAPI-1.7.4" PROJ="Rel. 4.8.0, 6 March 2012" GDAL="GDAL 1.9.1,
released 2012/05/15" LIBXML="2.8.0" LIBJSON="UNKNOWN" (core procs from "2.0.0
r9605" need upgrade) RASTER (raster procs from "2.0.0 r9605" need upgrade) |
2.0.1 r9979
> out-db rasters does have the limitation that they are read-only.
Good to know; shouldn't be a problem for us as model output is fundamentally
immutable. Any other limitations that I should be aware of?
~James
On Mon, Oct 29, 2012 at 05:05:03PM -0700, Bborie Park wrote:
> Wow. What version of PostGIS are you running?
>
> Great to hear that the out-db works for you. I always expected that
> out-db would work better for rasters with large numbers of bands.
> out-db rasters does have the limitation that they are read-only.
>
> -bborie
>
> On 10/29/2012 05:02 PM, James Hiebert wrote:
> >> I believe ST_Intersects() works on out-of-db rasters in the 2.0 series,
> >> possibly 2.0.1.
> >
> > Hmmm, for me it it fails for the (raster, integer, geometry) signature:
> >
> > raster_test=> SELECT rid FROM basins INNER JOIN bcsd ON ST_Intersects(rast,
> > 1, the_geom) WHERE rid = 39;
> > ERROR: rt_raster_intersects not implemented yet for OFFDB bands
> > CONTEXT: PL/pgSQL function "_st_intersects" line 20 at RETURN
> >
> > but it appears that you're right for the (geometry, raster, integer)
> > signature:
> >
> > raster_test=> SELECT rid FROM basins INNER JOIN bcsd ON
> > ST_Intersects(the_geom, rast, 1) WHERE rid = 39;
> > rid
> > -----
> > 39
> > (1 row)
> >
> >> I wonder what your benchmark's performance would be like if the raster
> >> is out-db. I'd expect a flat line with little change regardless the #
> >> of bands.
> >
> > Ah ha! Yes, that's definitely the case. With out of db storage, each of
> > intersects/clip queries comes back in < 200ms, regardless of num bands.
> > That's more of the behaviour that I was expecting, too. Thanks for helping
> > me put a finger on it!
> >
> > ~James
> >
> > On Mon, Oct 29, 2012 at 04:33:36PM -0700, Bborie Park wrote:
> >> I believe ST_Intersects() works on out-of-db rasters in the 2.0 series,
> >> possibly 2.0.1.
> >>
> >> As for performance of in-db vs out-db, in-db is slightly faster but my
> >> benchmarks are rather old. I hope to do some testing soon to see if I
> >> can improve out-db performance.
> >>
> >> Tile size is critical regardless of whether or not you're going to store
> >> your rasters in-db or out-db. Generally, tiles should be 100x100 or
> >> smaller. Ideal tile size depends upon the input raster's dimensions and
> >> what tile dimension is cleanly divisible from the raster's dimension.
> >>
> >> I wonder what your benchmark's performance would be like if the raster
> >> is out-db. I'd expect a flat line with little change regardless the #
> >> of bands.
> >>
> >> -bborie
> >>
> >> On 10/29/2012 04:23 PM, James Hiebert wrote:
> >>>> If you've got a large number of bands (100s or more), you may want to
> >>>> consider having the rasters be out-of-db.
> >>>
> >>> I had considered that (better, actually, than duplicating our data,
> >>> right?), but was finding that st_intersects wasn't yet implemented for
> >>> out of db storage. Looking through the trunk code, though, it appears
> >>> that maybe you've gone ahead and implemented that since 2.0.1? If so,
> >>> great! ST_PixelAsPoints() is another good reason for me to seriously
> >>> consider working out of trunk...
> >>>
> >>>> Part of the problem is that
> >>>> anything stored in PostgreSQL (in-db) is TOASTed so needs to be
> >>>> deserialized (and probably decompressed). So, if the serialized raster
> >>>> is big (more bands), the deTOASTing will take longer.
> >>>
> >>> Thanks; good to know.
> >>>
> >>>> Another problem with your benchmark query is that the ST_Clip() is
> >>>> running twice (for height and width).
> >>>
> >>> Ah, that changes the picture pretty dramatically (see attached plot).
> >>> Since it improves by a lot more than a factor of two, I suspect maybe I'm
> >>> having some desktop scaling issues or something. I'll go ahead and
> >>> actually put this on our database server, try the trunk version, and go
> >>> from there. This is at least somewhat encouraging :) Thanks for the
> >>> suggestions.
> >>>
> >>> ~James
> >>>
> >>> On Mon, Oct 29, 2012 at 03:50:04PM -0700, Bborie Park wrote:
> >>>> James,
> >>>>
> >>>> I use PostGIS raster for a similar purpose (model outputs) though my
> >>>> model outputs are for a specific day (average temperature for a specific
> >>>> date). So, one raster with one band per day per variable. I could
> >>>> combine a year's worth of bands into one raster but I decided against
> >>>> that.
> >>>>
> >>>> If you've got a large number of bands (100s or more), you may want to
> >>>> consider having the rasters be out-of-db. Part of the problem is that
> >>>> anything stored in PostgreSQL (in-db) is TOASTed so needs to be
> >>>> deserialized (and probably decompressed). So, if the serialized raster
> >>>> is big (more bands), the deTOASTing will take longer.
> >>>>
> >>>> Another problem with your benchmark query is that the ST_Clip() is
> >>>> running twice (for height and width).
> >>>>
> >>>> If you're in the evaluation stage and you're compiling PostGIS yourself,
> >>>> I'd recommend trying SVN -trunk (will become 2.1) as it has additional
> >>>> capabilities and performance improvements. I'm already using -trunk in
> >>>> production as I needed the new features (full disclosure: I wrote almost
> >>>> the new features in -trunk).
> >>>>
> >>>> -bborie
> >>>>
> >>>> On 10/29/2012 03:32 PM, James Hiebert wrote:
> >>>>> Hi All,
> >>>>>
> >>>>> I'm considering using PostGIS rasters for storage of raster data at my
> >>>>> organization and I'm looking for some advice (or perhaps a reality
> >>>>> check). I work for a region climate services provider and the vast
> >>>>> majority of our data (by volume, not necessarily complexity) are output
> >>>>> from climate models. These are generally a n-by-m raster with one band
> >>>>> for each timestep. There could be upwards of 36k to 72k timesteps for
> >>>>> a typical model run. We have hundreds of model runs.
> >>>>>
> >>>>> So my question is, is it insane to be thinking of storing that many
> >>>>> bands in a PostGIS raster? Or more specifically, is this _not_ a use
> >>>>> case for which PostGIS rasters were designed? I notice that most of
> >>>>> the examples in the docs and in "PostGIS In Action" focus only on
> >>>>> images and I can imagine that handling multispectral satellite images
> >>>>> as being more of the intended use case.
> >>>>>
> >>>>> I did a little benchmarking of a typical use case of ours ("What's the
> >>>>> average temperature inside a some polygon, e.g. a river basin?"). I
> >>>>> noticed that the run time for doing a ST_Clip(raster, band, geometry)
> >>>>> and ST_Intersects(raster, band, geometry) appears to be super-linear
> >>>>> even when doing it on just a single band. I ran the following query:
> >>>>> SELECT rid, st_height(st_clip(rast, 1, the_geom)),
> >>>>> st_width(st_clip(rast, the_geom)) FROM basins INNER JOIN bcsd ON
> >>>>> ST_Intersects(rast, 1, the_geom) WHERE rid = <rid> (where basins is
> >>>>> table of river basins with one single polygon and bcsd is a table with
> >>>>> a raster column "rast").
> >>>>> for a set of rasters with increasing number of bands, and the time to
> >>>>> run the query is shown in the attached plot. Since the raster
> >>>>> properties are presumably shared across all the bands, it seems odd to
> >>>>> me that run time would increase. I would expect it to be _contant_
> >>>>> (with constant number of pixels), but I suppose that that's my own
> >>>>> ignorance as to how the PG type extensions work?
> >>>>>
> >>>>> Comments or explanations are welcome.
> >>>>>
> >>>>> ~James
> >
>
> --
> Bborie Park
> Programmer
> Center for Vectorborne Diseases
> UC Davis
> 530-752-8380
> bkp...@ucdavis.edu
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--
James Hiebert
Lead, Computational Support
Pacific Climate Impacts Consortium
http://www.pacificclimate.org
Room 112, University House 1, University of Victoria
PO Box 1700 Sta CSC, Victoria, BC V8V 2Y2
E-mail: hieb...@uvic.ca
Tel: (250) 472-4521
Fax: (250) 472-4830
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